The present invention relates to a process for the preparation of cyclopropylamine from cyclopropanecarboxamide by the so-called Hofmann degradation.
Cyclopropylamine is an important intermediate in the preparation of biologically active substances.
The so-called Hofmann degradation, the rearrangement of acid amides with decarboxylation to give primary amines, is known in principle. This process has also already been used for the preparation of cyclopropylamine (DE-OS (German Published Specification) 1,939,759). In this, sodium hypochlorite solution is added at 0.degree. C. to a suspension of the cyclopropanecarboxamide in water; after the combination of the substances mentioned, a post-reaction time of 45 minutes is added on, likewise at 0.degree. C. After this, a 20 % strength sodium hydroxide solution is added with cooling and, after a further post-reaction time of 30 minutes, the reaction solution is at 45.degree.-50.degree. C. for 2 hours. Up to this point, at which only a storage-stable aqueous solution of cyclopropylamine is obtained, 4 hours pass. A 25-30 % strength aqueous solution of cyclopropylamine is obtained by working up by distillation. The degree of conversion is stated as 85-95%.
The relatively long total reaction time on the one hand and the side reactions occurring in spite of working at 0.degree. C. on the other hand, which are manifested in decreased yields, indicate the difficulties of this process.